Awww! This broke my heart. Seriously, this is so sweet. There will not be a dry eye in the house at your wedding. As for what to dance to, stick with songs with themes of support, loyalty and happiness.

It's cheesy, but "Wind Beneath My Wings" springs to mind. (The line "Did you ever know that you're my hero?" seems appropriate.)  Queen's "You're My Best Friend" is a great song that isn't too sappy that everyone will enjoy hearing. (There are some "honeys" in there, but it's pretty subtle.) Natalie Merchant's "Kind and Generous" (the song with the "Thank you/Thank you" chorus) is also sweet. The Pretenders "I'll Stand By You" can be spun in a non-romantic way. Elton John's "Daniel" (particularly if his name is Daniel).  "Whenever I Call You Friend" by Kenny Loggins and Steve Nicks. Many a father and daughter have danced to "What a Wonderful World," so that one could work. 

"Lean On Me" by Bill Withers is the best version of a classic song."You've Got a Friend In Me," from Toy Story, is cute and topical. And there's always Neil Diamond's "He Ain't Heavy, He's My Brother."

Van Morrison's "Have I Told You Lately" has some sweet lyrics ("You fill my heart with gladness/take away all my sadness/Ease my troubles, that's what you do"). The Rod Stewart version is the most famous (and most sappiest).

I've always liked "My Sister Rose" by 10,000 Maniacs, where the woman in the song is watching her sister get married. "Sister Honey" by Stevie Nicks is also nice.

Lots of Beatles songs would work. "In My Life," "With a Little Help From My Friends," "Yesterday." "We Are Family" by Sister Sledge is always fun.  

Coldplay's "Fix You" has moving, gender-neutral lyrics despite the fact that it was clearly written for Gwyneth Paltrow. ("When you try your best and you don't succeed...I will try to fix you.") "God Put a Smile Upon Your Face" could also work.

Growing up, my sister and I always liked Madonna's "Keep It Together," which has the line "Brothers and sisters/They've always been there for me." It's pretty upbeat.

Definitely pick something personal. Is there a song (or an artist) whom you both love? It doesn't necessarily have to be a popular song with obvious meaning. I went to a wedding recently where the couple danced to a song I had never heard before, but it was very sweet as it clearly had meaning to the both of them.

Any other song ideas? Oh, and congrats!